This invention relates generally to pocket spring assemblies, and in particular to pocket spring assemblies for use in cushions or mattresses. More specifically, the invention relates to apparatus and methods for efficiently producing pocket spring assemblies having a two-dimensional array of pocketed springs.
Most pocket spring assemblies are constructed of two-dimensional arrays of coil springs contained in individual fabric pockets. Such a construction is often referred to as the Marshall construction, being named after its inventor. Although the Marshall construction has provided a desirable level of cushioning performance for almost a century, its usage has been limited for a variety of reasons, primarily being limited by its high cost of manufacture.
For example, one common way of constructing pocket spring assemblies is by producing strings or linear arrays of pocketed springs which are subsequently joined together to form a two-dimensional array of pocketed springs. U.S. Pat. No. 4,234,983 describes one common way of forming strings of pocketed springs which can then be joined together to form a two-dimensional array of pocketed coils. Similar patents describing methods and apparatus for constructing strings of pocketed coils are U.S. Pat. Nos. 4,854,023 and 4,986,518. The complete disclosures of all these patents are herein incorporated by reference.
U.S. Pat. No. 4,578,834 describes techniques for joining strings of pocket springs to form a two-dimensional array of pocketed springs. In this patent, the strings of pocketed springs are connected to each other by an adhesive that is applied between lines of tangency of adjacent coil springs. A hot melt adhesive applicator transverses a string of pocketed coils, depositing a precise amount of adhesive on each coil jacket. A second string is positioned on the first, and pressure is applied thereto. The applicator then traverses the second string in the same manner as the first. The sequence is repeated until a spring assembly of desired size is created. The complete disclosure of this patent is herein incorporated by reference. U.S. Pat. No. 4,234,984 describes another method for joining adjacent strings of pocketed springs by alternately connecting the interior string of springs to the adjacent string on either side.
In summary, common prior art techniques for forming two-dimensional arrays of pocketed springs include the steps of forming strings of pocketed springs and then joining the strings together. Unfortunately, such a process is time consuming and inefficient, thereby increasing the cost of the pocket spring assembly. Hence, it would be desirable to provide a more efficient way to make a two-dimensional array of pocketed springs to thereby reduce the overall cost of the spring assembly. In particular, it would be desirable to provide a way to join strings of pocketed assemblies while the strings are being formed. In this way, a two-dimensional array of pocketed springs may be formed in a single, continuous process.
The invention provides exemplary fabric quilts, pocket spring assemblies, and apparatus and methods for producing such fabric quilts and pocket spring assemblies. The invention also provides exemplary mattresses incorporating such pocket spring assemblies. In one exemplary embodiment, a pocket spring assembly comprises a plurality of elongate fabric tubes disposed adjacent to each other. Each of the fabric tubes has a plurality of pockets into which a spring is disposed. Further, at least some of the pockets of adjacent fabric tubes are welded together at midpoints on the adjacent pockets, i.e. at locations where adjacent springs in adjacent tubes are closest to each other. Such a construction is preferably accomplished by welding together adjacent pockets utilizing welders which are disposed within the pockets. By utilizing a heat fusible material to construct the fabric tubes, the welder heat fuses the material together to produce an internal weld. In this manner, adjacent fabric tubes may be joined together just prior to depositing springs within each of the tubes so that the resulting pocket spring assembly is produced in a single, continuous process.
Each fabric tube preferably has a longitudinal axis, and each spring has a central axis about which the spring is coiled. The central axis of each spring is preferably oriented so that it is generally perpendicular to the longitudinal axis of the fabric tube. In one aspect, each fabric tube includes a plurality of closed segments which are spaced apart from each other to form the pockets. The closed segments preferably comprise welds that are generally perpendicular to the longitudinal axis of the fabric tubes.
The invention further provides an exemplary mattress which includes a pocket spring assembly having a plurality of elongate fabric tubes which each include a plurality of pockets into which springs are disposed. At least some of the pockets of adjacent tubes are welded together at midpoints on the adjacent pockets as described above. The mattress further includes at least one layer of padding material that is disposed on a top side of the spring assembly. A fabric cover is positioned over the spring assembly and the layer of padding material.
The invention also provides an exemplary method for producing a fabric quilt assembly. According to the method, a plurality of separate fabric tubes which are disposed laterally adjacent each other are simultaneously formed. A closed segment is simultaneously formed in each of the fabric tubes, and adjacent tubes are simultaneously joined together proximate the first closed segment.
In one aspect, the adjacent tubes are joined by welding the adjacent fabric tubes from within the fabric tubes. In another aspect, the closed segments are formed and the adjacent tubes are joined at substantially the same time.
The invention still further provides an exemplary method for producing a pocket spring assembly. According to the method, a plurality of fabric tubes are formed. A first closed segment is formed in each of the fabric tubes, and adjacent tubes are joined proximate to the first closed segment. A spring is placed adjacent to the first closed segment of each fabric tube. Preferably, the adjacent tubes are joined together before placement of the springs adjacent to the first closed segment. A second closed segment is then formed in each of the fabric tubes in a manner such that the springs are disposed between the first and the second closed segments in a fabric pocket. Once each fabric has received a first spring, a second spring is placed behind the second closed segment after first joining adjacent tubes proximate to the second closed segment. A third closed segment is then formed in each of the fabric tubes behind the second springs. This process is then repeated as many times as needed to produce the desired size of the pocket spring assembly. In this manner, a way is provided to produce a two-dimensional array of pocketed springs in a continuous process.
In one particularly preferable aspect, adjacent tubes are joined together by welding the adjacent fabric tubes from within the fabric tubes. In this way, the two-dimensional array of pocketed springs may be formed in a continuous process, without the need to separately join strings of pocketed springs as with conventional prior art techniques.
In another particular aspect, the method utilizes a plurality of parallel guide members which each has a longitudinal axis and a longitudinally oriented channel. In this way, at least a section of each of the fabric tubes is placed over the guide members, and the springs are introduced through the channels until they exit the guide members and expand within the fabric tubes. Preferably, the adjacent tubes are joined together while the fabric tubes remain over the guide members to allow the pocket spring assembly to be formed in situ. For example, the fabric tubes are preferably advanced over guide members after a spring has been inserted and the second closed segment has been formed so that an additional row of springs may be introduced through the guide members and a closed segment formed behind each of the springs in the row.
Each of the springs has a central axis about which the springs are coiled, and the central axis of each spring is preferably perpendicular to the longitudinal axis of the guide members when introduced through the channels. Further, the first and the second closed segments are preferably produced by welds that are generally perpendicular to the longitudinal axis. In another aspect, each fabric tube is formed from a single piece of fabric. Preferably, two side edges of each piece of fabric are welded together along a longitudinal line to form the fabric tubes.
The invention also provides an exemplary apparatus for producing a pocket spring assembly. The apparatus comprises a plurality of parallel guide members which each have a longitudinal axis and a longitudinally oriented channel. The guide members are each configured to be received into at least a section of a fabric tube. An advancement mechanism is provided to selectively advance the fabric tubes over the guide members. The apparatus also includes a dispensing mechanism to dispense compressed springs through the channels and into the fabric tubes. When dispensed, a central axis of the springs is perpendicular to the longitudinal axis. A connection mechanism is provided to produce closed segments in the fabric tubes to form a fabric pocket around each spring. Further, a joining mechanism is provided to join adjacent fabric tubes before dispensing of the springs. In this way, an apparatus is provided for producing a two-dimensional array of pocketed springs in situ, i.e., while at least a portion of the fabric tubes remain over the guide members.
In one particular aspect, a compression mechanism is provided to compress the springs so that they may be inserted through the channels. The apparatus preferably also includes at least one folding element that is associated with each guide member. The folding element is configured to form a piece of fabric into one of the fabric tubes. Fabric welding mechanisms are preferably also provided to weld two ends of the pieces of fabric together to form the fabric tubes.
In one particularly preferable aspect, the connection mechanisms each comprise a pair of jaws to produce a weld in the tubular fabric sections generally perpendicular to the longitudinal axis. The joining mechanisms preferably each comprise welders to produce welds between the adjacent tubular fabric sections, with the welds being made from within the tubular fabric sections.